As wireless and wired network connectivity is rapidly expanding and the number of network users is steadily increasing, there has been great momentum in the multimedia industry for supporting content display in a wide variety of network connected devices. This is complicated, however, due to the great diversity of devices with various display resolutions. The range of devices includes both standard and high-definition computer monitors with large displays, and smart phone devices with smaller displays. Accordingly, it is often necessary to down-sample an image to a size which may be displayed on a given device. Down-sampling may also be desirable in order to minimize the bandwidth or time required to transfer an image over a network. This is particularly a concern where the image is being transferred over a wireless medium.
Many image and video types represent images or video in a Discrete Cosine Transform (“DCT”) domain. For example the IPEG, MPEG, DV and MJPEG image and video types represent images or videos in the DCT domain. Where the image or video is represented in a DCT domain, down-sampling is particularly difficult.
Typically, down-sampling a DCT image or video involves first converting DCT data to a spatial domain using an inverse DCT operation and applying a standard down-sampling method in the spatial domain. After the image is down-sampled in the spatial domain it is typically converted back to the DCT domain using a DCT operation. Due to the use of the DCT and the inverse DCT, methods which down-sample a DCT image or video by first converting it back to the spatial domain typically have a large computational complexity. A large computational complexity results in a longer calculation and a calculation which utilizes more processor time and power.
Similar reference numerals are used in different figures to denote similar components.